1. Field of the Invention
The present invention relates to an improved method and system for coating materials as well as improved protective coatings for materials. Particularly, the present invention is directed to a method and system for making a coating including cobalt, phosphorous and particles of material having superior tribological characteristics.
2. Description of Related Art
Electroplated hard chrome coating is widely used as a wear resistant coating to prolong the life of mechanical components. However, conventional hard chrome electroplating processes generate hexavalent chromium ion which is a known carcinogen. Hence, there is a major effort throughout the electroplating industry to replace hard chrome coatings with an environmentally benign, non-carcinogenic coating having characteristics similar or superior to those of hard chrome.
Thermal spray hard coatings of chromium carbide, tungsten carbide, tribaloy, aluminum oxide and the like, using Plasma Spray, High Velocity Oxy Fuel (HVOF) and other similar processes are currently being used to replace hard chrome coatings. However, these processes have not been able to be used for non line of sight (NLOS) applications, such as the inner diameter (ID) of cylinders, bearing cavities and the like. Even for the outer surface applications, thermal spray coatings are generally deposited in thick layers and later ground to a desired thickness. Hence, thermal sprayed coatings are generally more expensive than electroplated hard chrome.
For NLOS applications, a number of electroplated coatings have been evaluated. These include electroplated Ni—P and Ni—W alloy coatings, Ni—SiC electrocomposite and other similar coatings. However, none of these coatings have all the desired characteristics of hard chrome. Also, nickel base coatings are now considered undesirable because it has been found that in some cases they can cause severe allergic reactions.
Recently, a new nanocrystalline Co—P base coating has been developed by pulse plating processes. The resulting nanocrystalline Co—P coating appears to be a very promising replacement for hard chrome as its characteristics are either equal or superior to those of hard chrome. However, the electroplating process for this nanocrystalline Co—P base coating is based on pulse plating. In pulse plating, the applied voltage between the anode and cathode is pulsed at different amplitudes and at various frequencies. This pulse plating process used to produce nanocrystalline Co—P coatings requires special power supplies which are currently available only for laboratory research and development. Large scale affordable pulsed power supplies for the production environment are not currently available. Hence, there is a continued need for improved coatings and associated processes for replacing hard chrome. The present invention provides a solution for these and other problems.